The present invention relates to a compact electric motor that is used in an environment where ingress of grease or oil is problematic, and also to an electric appliance such as ABS or the like utilizing such compact electric motor and an electric machine tool.
In recent years, the compact electric motor utilized in electric appliances and electric machine tools is required to have a high reliability while having lightweight and compact features.
The conventional compact electric motor is shown in FIG. 10. Referring to FIG. 10, reference numeral 1 represents a compact electric motor, reference numeral 2 represents a winding, reference numeral 3 represents an output shaft, reference numeral 4 represents an iron core, reference numeral 5 represents a brush, reference numerals 6 and 11 represent a bearing, reference numeral 7 represents a commutator, reference numeral 8 represents a rotor, reference numeral 9 represents a yoke, reference numeral 10 represents a bracket, reference numeral 12 represents a brush holder, and reference numeral 13 represents a permanent magnet.
The rotor 8 of the compact electric motor 1 is constituted by the iron core 4 of a generally circular shape having a plurality of slots, the winding 2 coiled and accommodated within the slots, the output shaft 3 extending axially through a center of the iron core 4 and fixed in position, and the commutator 7 fixed on the output shaft 3 and to which opposite ends of the winding 2 are electrically connected. This rotor 8 is covered by the yoke 9 of a close-ended hollowly cylindrical shape for rotatably accommodating the rotor 8 and having an inner peripheral surface on which a plurality of permanent magnets 13 are fixedly mounted. The bracket 10 is mounted to close an opening end of the yoke 9. This compact electric motor 1 of the structure described above is provided with the brush holder 12 inside the bracket 10 and the brush 5 accommodated in the brush holder 12 is slidingly engaged with the commutator 7.
However, with the above described construction, in the event of leakage of grease from a bearing on one side adjacent the output shaft or ingress of oil from a counterpart machine, there is a high possibility that it will deposit on the commutator and/or the brush, resulting in an abnormal wear of the brush and reduction in performance of the compact electric motor.
The present invention is intended to provide a compact electric motor effective to provide a high reliability against the leakage of grease from a bearing on one side adjacent the output shaft or the ingress of oil from a counterpart machine.
The compact electric motor according to the present invention is such that the bracket or the brush holder has a wall having a predetermined gap around the output shaft between the commutator and the bearing.
Thereby, in the event of leakage of grease from the bearing on one side adjacent the output shaft or ingress of oil from the counterpart machine, it is possible to prevent deposition on the commutator and the brush and, hence, to avoid an abnormal wear of the brush and reduction in performance of the compact electric motor and, accordingly, a high reliability as the compact electric motor that is used in such application can be obtained.
More specifically, the invention described in claim 1 of the present invention is a compact electric motor comprising: a rotor having a generally circular iron core with a plurality of slots, a winding wound and accommodated in the slots, an output shaft extending axially through a center of the iron core and fixed there and a commutator fixed on the output shaft and to which opposite ends of the winding are electrically connected; a casing (yoke) of a generally close-ended hollow cylindrical shape rotatably accommodating the rotor and having a plurality of permanent magnets fixed to an inner peripheral surface thereof; a bearing for rotatably supporting the output shaft; a bracket mounted to close an opening end of the casing with the output shaft penetrating through the bracket, and provided with a housing for accommodating the bearing; a brush slidingly engaged with the commutator; a brush holder disposed inside the bracket and accommodating the brush, characterized in that the bracket is provided with: a wall extending between the commutator and the bearing and having a predetermined gap around the shaft; a recessed portion formed at a portion of periphery of the housing and hollowing inward in the casing; a depleted portion formed by depleting a portion of the housing so as to allow a space between the bearing accommodated in the housing and the wall to be in communication with a recessed portion and, therefore, in the event of grease leakage from the output side bearing or ingress of oil from the counterpart machine, deposition on the commutator and the brush is prevented and abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented to thereby provide the compact electric motor of a high reliability. Furthermore, there is an advantage that since when the amount of oil flowing into the compact electric motor increases, it flows from the depleted portion into the recessed portion there is no possibility of oil entering over the wall into the compact electric motor and, therefore, deposition on the commutator and the brush is prevented and abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented to thereby provide the compact electric motor of a high reliability.
The invention described in claim 2 of the present invention is a compact electric motor comprising: a rotor having a generally circular iron core with a plurality of slots; a winding wound and accommodated in the slots, an output shaft extending axially through a center of the iron core and fixed thereto, and a commutator fixed on the output shaft and to which opposite ends of the winding are electrically connected; a casing (yoke) of a generally close-ended hollow cylindrical shape rotatably accommodating the rotor and having a plurality of permanent magnets fixed to an inner peripheral surface thereof; a bearing for rotatably supporting the output shaft; a brush slidingly engaged with the commutator; a brush holder disposed adjacent to an opening end of the casing and accommodating the brush, characterized in that the brush holder is constructed so as to close the opening end of the casing with the output shaft penetrating through the brush holder while accommodating the brush, and is provided with; a housing for accommodating the bearing; a wall extending between the commutator and the bearing and having a predetermined gap around the shaft; a recessed portion formed at a portion of periphery of the housing and hollowing inward in the casing; a depleted portion formed by depleting a portion of the housing so as to allow a space between the bearing accommodated in the housing and the wall to be in communication with a recessed portion and, therefore, in the event of grease leakage from the output side bearing or ingress of oil from the counterpart machine, deposition on the commutator and the brush is prevented and abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented to thereby provide the compact electric motor of a high reliability. Furthermore, there is an advantage that the number of component parts can be reduced and compactization and reduction in weight are possible since the brush holder has the housing for accommodating the bearing, which closes the opening end of the casing with the output shaft penetrating through the housing. Still further, there is an advantage that since when the amount of oil flowing into the compact electric motor increases, it flows from the depleted portion into the recessed portion, there is no possibility of oil entering over the wall into the compact electric motor and, therefore, deposition on the commutator and the brush is prevented and abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented to thereby provide the compact electric motor of a high reliability.
The invention described in claim 4 is characterized in that a shaft side end of the wall is provided with a projection protruding towards the bearing along the output shaft in the compact electric motor as claimed in any of claims 1 to 3 and, therefore, there is an advantage that there is no possibility of oil entering over the wall into the compact electric motor and, therefore, deposition on the commutator and the brush is prevented and abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented to thereby provide the compact electric motor of a high reliability.
The invention described in claim 6 is characterized in that a breathing hole is formed by depleting a portion of the housing opposite to the depleted portion of the housing for allowing a space formed between the bearing accommodated in the housing and the wall to be in communication with a space out of the motor in the compact electric motor as claimed in any of claims 1 to 4 and, therefore, there is an advantage that formation of an oil film in the depleted portion can be prevented to allow it to flow into the recessed portion and there is no possibility of the oil flowing over the wall into the compact electric motor and, therefore, deposition on the commutator and the brush is prevented and abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented to thereby provide the compact electric motor of a high reliability.
The invention described in claim 7 is characterized in that the recessed portion is provided so that it is located in a lower region beneath the brush accommodated in the brush holder in a vertical direction in a motor""s mounted state in the compact electric motor as claimed in any of claims 1 to 6 and, therefore, there is an advantage that deposition on the commutator and the brush can be prevented even though the amount of oil or the like leaking into the compact electric motor is excessively so large as to overflow from the recessed portion and, therefore, the abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented to thereby provide the compact electric motor of a high reliability.
The invention described in claim 8 is characterized in that a second wall is provided which is fastened or formed integrally with the shaft between the bearing and the wall having a predetermined gap around the shaft, the second wall extending along the wall having a predetermined gap around the shaft in the compact electric motor as claimed in any of claims 1 to 7 and, therefore, there is an advantage that since the labyrinth shape of the wall is taken relative to a mist of oil during the elevated temperature, ingress into inside the compact electric motor can be prevented and therefore, the abnormal wear of the brush and reduction in performance of the compact electric motor can be prevented, thereby to provide the compact electric motor of a high reliability.
The invention described in claim 9 is an electric appliance characterized by having the electric compact motor as claimed in any of claims 1 to 8 and, therefore, there is an advantage that the electric appliance having a high reliability can be obtained.
The invention described in claim 10 is characterized in that the electric appliance as claimed in claim 9 is an ABS device and, therefore, there is an advantage that the electric appliance having a high reliability can be obtained.
The invention described in claim 11 is an electrically driven machine tool characterized by having the electric compact motor as claimed in any of claims 1 to 8 and, therefore, there is an advantage that the electrically driven machine tool of a high reliability can be obtained.